Issue is as follows.
Boot and running is fine, as soon as a USB stick is plugged into any USB port I get this error.Hardware Malfunction Results in System Error Message
I have unplugged everything except the motherboard, screen, original RAM, hard drive and power supply but still get this error when I plug in a USB. Trouble is there are 2 USB ports hard wired onto the motherboard at the back so I can't isolate the USB slots to replace them. I have unplugged the other two USB ports that are on a seperate board with a ribbon cable to no effect.
Anyone know of a possible solution to this without replacing the whole motherboard?

Yep multiple USB sticks.
A wired mouse and wireless keyboard+mouse does not cause the crash.
A USB stick when left plugged in during startup will not cause the crash but cannot access the USB stick.
Latest drivers are installed and a fresh install on Windows XP has also been done.